Overhead electric power distribution lines are supported on utility poles that may be 40-50 feet high. Horizontal supports mounted to the pole often carry various distribution apparatus. Because such distribution lines commonly operate in a three-phase system with three lines mechanically connected to the horizontal support and electrically insulated from each other, three associated lines ordinarily must be switched and reconnected simultaneously for maintenance or rerouting of power. This simultaneous switching process requires some form of group operated switch system.
Currently, many high voltage switch assemblies for overhead power distribution lines are open and closed by a field technician using a hookstick. The hookstick engages an operating lever connected to a universal control section securely connected to the rotatable switch phase bearing. Rotation of the bearing is translated into lateral displacement of an interphase shaft along the horizontal support beam. Conductive switch blades on each switch phase connection may be rotated into or out of electrical connection with the respective phase line. Pulling a hook on the operating lever with the hookstick rotates the control shaft, which rotates the switch blades into either closed or open positions.
High voltage overhead power switches are typically mounted well above ground and experience a variety of externally applied forces, such as weather, wild animals, vandalism, utility pole deformation, and vibration, which may cause a switch blade to move or close unintentionally. Furthermore, if a switch blade moves close enough to a contact, flashover may occur. The operating lever must maintain the security required to prevent unintended closing, opening or movement of the conductive blades. Therefore, a need exists for an overhead switch assembly having a resistance assembly to prevent accidental closing, opening or movement of the switch blades.
Accidental closing of a switch blade may cause equipment damage, loss of electrical service and personnel injury. Therefore, a need exists for a resistance assembly to secure a switch assembly in an open position. A further need exists for a resistance assembly for high voltage three phase distribution systems that provides resistance forces to maintain the switchblades in an opened or closed position despite ambient wind, weather, and vibration.
Existing switch assemblies generally require positive measures to be taken to ensure that the switch assembly is locked and prevented from operating. U.S. Pat. No. 5,451,730 to Phillips, Sr.; U.S Pat. No. 5,467,622 to Becker et al.; and U.S. Pat. No. 5,260,528 to Benda disclose switch assemblies in which an operator must manually lock the switch in an open or closed position. Thus, a need exists for a resistance assembly that secures a switch assembly in an open or closed position without requiring the operator to manually lock the switch assembly in that position.
A need exists for an improved resistance assembly to secure a switch assembly in an open or closed position.